> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ai-stats.phaseo.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Mistral: Mistral Small 3.2 to Mistral Small 4

> Gateway migration notes for upgrading Mistral Small traffic to Mistral Small 4, including reasoning_effort behavior.

# Mistral: Mistral Small 3.2 to Mistral Small 4

Use this guide when migrating Mistral Small routes to:

* `mistral/mistral-small-4-2026-03-16`

Previous common route:

* `mistral/mistral-small-3-2-2025-06-20`

## What changed

* Mistral Small 4 exposes a reasoning mode control via `reasoning_effort`.
* Gateway sends only two upstream values for this model route:
  * `none` (reasoning off)
  * `high` (reasoning on)
* Gateway normalizes Mistral thinking blocks back into standard response fields:
  * `message.content` for assistant-visible text
  * `message.reasoning_content` and `message.reasoning_details` for reasoning text

## Required request changes

Reasoning defaults to off for this route.

Gateway mapping rules:

* if you omit reasoning controls, Gateway sends `reasoning_effort: "none"`
* if you pass `reasoning.enabled: true`, Gateway sends `reasoning_effort: "high"`
* if you pass `reasoning.effort: "none"`, Gateway sends `reasoning_effort: "none"`
* if you pass any other `reasoning.effort` value, Gateway sends `reasoning_effort: "high"`

Recommended usage:

* use `reasoning.effort: "none"` for lightweight behavior
* use `reasoning.effort: "high"` for deep reasoning

Example:

```json theme={null}
{
  "model": "mistral/mistral-small-4-2026-03-16",
  "messages": [
    { "role": "user", "content": "Why is fast inference important?" }
  ],
  "reasoning": {
    "effort": "high"
  }
}
```

## Response handling notes

Mistral may return mixed assistant content blocks (for example `thinking` + `text`). Gateway maps that into a stable shape so you can consume:

* final user-visible answer from `choices[0].message.content`
* reasoning text from `choices[0].message.reasoning_content`

This lets you preserve downstream behavior that expects OpenAI-style chat completion fields.

## Rollout checklist

1. Update model ID to `mistral/mistral-small-4-2026-03-16`.
2. Validate reasoning controls using only `none` and `high`.
3. Re-run output quality and schema tests on your high-effort routes.
4. Compare latency/cost for `none` vs `high` before full cutover.